Non-Fouling Surfaces for Reflective Spheres

ABSTRACT

The present invention relates to treating of reflective surfaces to prevent fouling. The present invention also relates to reflective materials treated to prevent fouling, as well as methods of using such reflective materials.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional of U.S. patent application Ser.No. 12/432,264, filed Apr. 29, 2009, which claims the benefit of U.S.Provisional Patent Application No. 61/071,477, filed Apr. 30, 2008, thedisclosure of which is incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to treating of reflective surfaces toprevent fouling. The present invention also relates to reflectivematerials treated to prevent fouling, as well as methods of using suchreflective materials.

2. Background of the Invention

Reflective or retroreflective materials often fail to achieve optimalperformance when the surface of such materials is stained or fouled byexternally applied contaminants such as fluids (including biologicalfluids) or soluble dirt. Fouling of such surfaces reduces the reflectiveproperties of these materials. Therefore, use of reflective materials inenvironments where fouling can occur, for example, in “dirty”environments (e.g., industrial applications, rain, high humidity) or inthe body (or in contact with bodily fluids, e.g., during surgicalprocedures) is greatly impeded by the loss of reflectivecharacteristics.

What are needed therefore are methods for preventing or limiting foulingof reflective surfaces, thereby maintaining their reflective properties.

BRIEF SUMMARY OF THE INVENTION

The present invention fulfills the needs noted above by providingmethods for disposing a liquidphobic structure on the surface of areflective material so as to limit or prevent fouling of the reflectivematerial, while still maintaining its reflective characteristics.Reflective materials comprising such liquidphobic materials are alsoprovided.

In an embodiment, the present invention provides reflective substratescomprising a liquidphobic structure on a surface of the substrate.Suitably, the substrate substantially maintains its reflectiveproperties after the substrate is contacted with a liquid (e.g., abiological fluid). Exemplary reflective substrates include reflectivefilms, reflective marker dots, reflective tapes, reflective fabrics,retroreflective materials, reflective spheres and reflective cubes.

In suitable embodiments, the liquidphobic structure comprises ahydrophobic coating, including a hydrophobic coating that directlycontacts the surface of the substrate. In other embodiments, thehydrophobic coating is disposed on a sub-micron structured surface ofthe substrate. Exemplary hydrophobic coatings for use in the practice ofthe present invention include, but are not limited to, perfluorinatedorganics. Suitably the substrate maintains at least 70% of itsreflective properties after contact with a liquid.

In further embodiments, the present invention provides methods ofsubstantially maintaining the reflective properties (suitably at least70% of the reflective properties are maintained) of a reflectivesubstrate. Suitably, such methods comprise disposing a liquidphobicstructure on a surface of the substrate, wherein the reflectiveproperties are substantially maintained after the substrate is contactedwith a liquid (e.g., a biological fluid).

Suitably, the methods comprise disposing a hydrophobic coating on thereflective substrate, for example, disposing a hydrophobic coatingdirectly onto the surface of the substrate. In further embodiments, themethods comprise generating a sub-micron-structured surface on thesurface of the substrate and disposing a hydrophobic coating (e.g., aperfluorinated organic coating) onto the sub-micron-structured surface.For example, the methods comprise generating a sub-micron-structuredsurface by disposing a layer of silica particles (suitably sub-micronsilica particles) on the reflective substrate. A hydrophobic coatingcomprising a perfluorinated silane coating can then be disposed on thesilica particles.

In further embodiments, the present invention provides methods ofdisposing a liquidphobic structure on a reflective substrate, comprisinggenerating a sub-micron-structured surface (e.g., a layer of sub-micronsilica particles) on the reflective substrate and disposing aliquidphobic structure (e.g., a perfluorinated silane coating) on thesub-micron-structured surface.

In additional embodiments, the present invention provides reflectivespheres comprising a hydrophobic coating (e.g., a perfluorinatedorganic) on a surface of the sphere, wherein the sphere substantiallymaintains its reflective properties (suitably at least 70% of itsreflective properties) after the sphere is contacted with a liquid(e.g., a biological fluid). In suitable embodiments, the surface of thesphere further comprises a sub-micron-structured layer of silicaparticles and a perfluorinated silane hydrophobic coating.

In still further embodiments, the present invention provides methods ofperforming a medical procedure using a surgical navigation system on apatient.

Additional features and advantages of the invention will be set forth inthe description that follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theadvantages of the invention will be realized and attained by thestructure and particularly pointed out in the written description andclaims hereof as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The accompanying drawings, which are incorporated herein and form a partof the specification, illustrate the present invention and, togetherwith the description, further serve to explain the principles of theinvention and to enable a person skilled in the pertinent art to makeand use the invention.

FIGS. 1A-1C show reflective materials comprising liquidphobic structuresin accordance with embodiments of the present invention.

FIGS. 2A-2B show the effect of fouling (2A) on a reflective substrate,and the use of a liquidphobic structure (2B) to prevent fouling andmaintain the reflective characteristics of a material.

FIGS. 3A-3B show reflective spheres in accordance with one embodiment ofthe present invention.

The present invention will now be described with reference to theaccompanying drawings. In the drawings, like reference numbers indicateidentical or functionally similar elements.

DETAILED DESCRIPTION OF THE INVENTION

It should be appreciated that the particular implementations shown anddescribed herein are examples of the invention and are not intended tootherwise limit the scope of the present invention in any way. Indeed,for the sake of brevity, conventional electronics, manufacturing,semiconductor devices, and nanocrystal, nanoparticle, nanowire (NW),nanorod, nanotube, and nanoribbon technologies and other functionalaspects of the systems (and components of the individual operatingcomponents of the systems) may not be described in detail herein.

U.S. Patent Application Pub. 20050181195 and U.S. patent applicationSer. No. 11/869,508, filed Oct. 9, 2007, are incorporated by referenceherein in their entireties for all purposes. These applications relatein part to various methods of forming liquidphobic surfaces.

As used herein, the term “nanostructure” refers to a structure that hasat least one region or characteristic dimension with a dimension of lessthan about 500 nm, including on the order of less than about 1 nm. Asused herein the terms “sub-micron-structure” and “sub-micron-structured”refers to a structure that has at least one region or characteristicdimension with a dimension of less than about 1 μm. As used herein, whenreferring to any numerical value, “about” means a value of ±10% of thestated value (e.g. “about 100 nm” encompasses a range of sizes from 90nm to 110 nm, inclusive). The term “nanostructure” as used hereinencompasses nanoparticles, quantum dots, nanocrystals, nanowires,nanorods, nanoribbons, nanofibers, nanotubes, nanotetrapods and othersimilar nanostructures known to those skilled in the art. As describedthroughout, nanostructures (including nanoparticles, nanocrystals,nanofibers, quantum dots, nanowires, etc.) suitably have at least onecharacteristic dimension less than about 500 nm. Suitably,nanostructures are less than about 500 nm, less than about 300 nm, lessthan about 200 nm, less than about 100 nm, less than about 50 nm, lessthan about 20 nm, less than about 15 nm, less than about 10 nm or lessthan about 5 nm in at least one characteristic dimension (e.g., thedimension across the width or length of the nanostructure).

In one embodiment, the present invention provides reflective substratescomprising a liquidphobic structure on a surface of the substrate,wherein the substrate substantially maintains its reflective propertiesafter being contacted with a liquid.

As shown in FIG. 1A, suitably reflective substrate 102 comprises aliquidphobic structure 104 on at least one surface of substrate 102. Asused herein the term “reflective substrate” refers to a material thathas at least one surface that reflects light. Reflective substrates alsoinclude “retroreflective substrates” which send light or other radiationback in the same direction it initiated from, regardless of the angle ofincidence. Light that can be reflected by the various reflectivesubstrates include visible light, as well as non-visible lightincluding, but not limited to, infrared and ultraviolet wavelengths.Exemplary reflective substrates that can be utilized in the practice ofthe present invention include various films, paints, reflective markerdots, tapes, fabrics and coatings, as well as various structures, suchas reflective objects, including reflective spheres, cubes (or any othershape). Reflective substrates also include materials that have areflective coating or layer on their surface. The terms “reflectivesubstrate” and “reflective material” are used interchangeablythroughout.

As used herein, the term “liquidphobic structure” includes liquidphobiccoatings, films, layers and portions of such coatings, films and layers.That is, a liquidphobic structure need not completely cover the surfaceof a reflective substrate, and in suitable embodiments, may cover only aportion of the surface. However, suitably, at least a majority, if notall, of the surface of reflective material that will be reflecting lightwill be covered with a liquidphobic structure. In further embodiments, apatterned surface can be generated in which portions or sections of thesurface comprise a liquidphobic structure, while other portions do not(e.g., hydrophobic and non-hydrophobic sections).

As used herein, “liquidphobic” or “super-liquidphobic” structuresdescribe, in a general sense, any material that displays anti-liquidproperties, e.g., a material that is one or more of hydrophobic (repelswater), lipophobic (repels oils and lipids), amphiphobic (a materialwhich is both hydrophobic and lipophobic), hemophobic (repels blood orblood components) or the like. Such materials repel liquids, e.g., bycausing the liquid to bead-up on the material's surface and not spreadout or wet the material's surface. Thus, as used herein, a substratethat is described as comprising a liquidphobic structure includessubstrates that comprise a liquidphobic, super-liquidphobic,hydrophobic, super-hydrophobic, amphiphobic and/or super-amphiphobicsubstrate.

When a drop of a liquid (e.g., water based, lipid based, etc.) restsupon a surface, it will spread out over the surface to a degree basedupon such factors as the surface tensions of the liquid and thesubstrate, the smoothness or roughness of the surface, etc. For example,the liquidphobicity of a substrate can be increased by various coatingsthat lower the surface energy of the substrate. The quantification ofliquidphobicity can be expressed as the degree of contact surface angle(or contact angle) of the drop of the liquid on the surface.

For example, for a surface having a high surface energy (i.e., higherthan the surface tension of the liquid drop), a drop of liquid willspread out “wetting” the surface of the substrate. Such surface displaysliquidphilicity, as opposed to liquidphobicity. When the surface energyof a substrate is decreased, liquidphobicity is increased (and viceversa). Liquidphobic, including hydrophobic, lipidphobic and/oramphiphobic refer to properties of a substrate which cause a liquid dropon their surface to have a contact angle of 90° or greater.“Super-hydrophobicity,” “super-amphiphobicity,” and“super-liquidphobicity” all refer to properties of substances whichcause a liquid drop on their surface to have a contact angle of 150° orgreater.

In suitable embodiments, the liquidphobic structure on the reflectivesubstrate is a hydrophobic structure, such as a hydrophobic coating orfilm (e.g., a coating that repels water). As shown in FIG. 1A, suitablyliquidphobic structure 104 (e.g., a hydrophobic coating) is directly incontact with the surface of reflective material 102. In suitableembodiments, the surface of reflective substrate 102 will comprise asub-micron structured surface 106, for example, if the reflectivesubstrate comprises reflective microspheres or a similar structure onits surface as in FIG. 1B, onto which a liquidphobic structure 104 isdisposed.

Exemplary liquidphobic structures for use in the practice of the presentinvention include various chemical coatings and films, including thoseshown below in Table 1. The liquidphobic structure suitably generates anoptically clear coating or layer on the reflective substrate so as tonot impede or impair the passage of light to and from the reflectivesurface.

Examples of compounds that can be used to coat the reflective substratesof the present invention beyond those listed in Table 1 are well knownto those of skill in the art. Many of the exemplary liquidphobiccompounds (including, e.g., hydrophobic, lipophobic, amphiphobiccompounds, etc.) in Table 1 can be found in common commercial sourcessuch as chemical catalogues from, e.g., United Chemicals, Sigma-Aldrich,etc. In exemplary embodiments, the reflective substrates can befluorinated, e.g., treated with a perfluorinated organic compound, suchas a perfluorinated silane, e.g., a fluoroalkylsilane group, etc.Exemplary liquidphobic compounds include those created through treatmentwith silane agents, heptadecafluorodecyltrichlorosilane,perfluorooctyltriclorosilane, heptadecafluorodecyltrimethoxysilane,perfluorododecyltrichlorosilane, perfluorinated carbon chains (e.g.,perfluorooctyl trichlorosilane), polyvinyliden fluoride,polyperfluoroalkyl acrylate, octadecanethiol, fluorine compounds (e.g.,graphite fluoride, fluorinated monoalkyl phosphates, C₄F₈, etc.), etc.In other embodiments, the liquidphobic structures can comprise coatingsof fluorocarbons, Teflon®, silicon polymers (e.g., Hydrolam 100®),polypropylene, polyethylene, wax (e.g., alkylketene dimers, paraffin,fluorocarbon wax, etc.), plastic (e.g., isotactic polypropylene, etc.),PTFE (polytetrafluoroethylene), diamond and diamond-like surfaces, aswell as inorganic materials. Additional exemplary liquidphobicstructures/coatings are listed below in Table 1.

TABLE 1 Liquidphobicity Functionality Chemical Name Hydrophobic C2Ethyltrichlorosilane Hydrophobic C2 Ethyltriethoxysilane Hydrophobic C3n-Propyltrichlorosilane Hydrophobic C3 n-PropyltrimethoxysilaneHydrophobic C4 n-Butyltrichlorosilane Hydrophobic C4n-Butyltrimethoxysilane Hydrophobic C6 n-HexyltrichlorosilaneHydrophobic C6 n-Hexyltrimethoxysilane Hydrophobic C8n-Octyltrichlorosilane Hydrophobic C8 n-Octyltriethoxysilane HydrophobicC10 n-Decyltrichlorosilane Hydrophobic C12 n-DodecyltrichlorosilaneHydrophobic C12 n-Dodecyltriethoxysilane Hydrophobic C18n-Octadecyltrichlorosilane Hydrophobic C18 n-OctadecyltriethoxysilaneHydrophobic C18 n-Octadecyltrimethoxysilane Hydrophobic C18 Glassclad-18Hydrophobic C20 n-Eicosyltrichlorosilane Hydrophobic C22n-Docosyltrichlorosilane Hydrophobic Phenyl PhenyltrichlorosilaneHydrophobic Phenyl Phenyltriethoxysilane Amphiphobic Tridecafluorooctyl(Tridecafluoro-1,1,2,2,- tetrahydrooctyl)-1-trichlorosilane AmphiphobicTridecafluorooctyl (Tridecafluoro-1,1,2,2,- tetrahydrooctyl)-1-triethoxysilane Amphiphobic Fluorinated alkanes Fluoride containingcompounds Alkoxysilane PTFE hexamethyldisilazane Aliphatic hydrocarboncontaining compounds Aromatic hydrocarbon containing compounds Halogencontaining compounds Paralyene and paralyene derivatives Fluorosilanecontaining compounds Fluoroethane containing compounds

As discussed throughout, contact between a liquid and a reflectivematerial can result in fouling or otherwise contamination of the surfaceof a reflective material. Fouling can occur when a reflective materialis contacted with a liquid, often containing various unwantedcontaminants, such as dirt, debris, oils, salts, lipids, or biologicalfluids such as blood, urine, saliva, marrow, fat, etc., which containvarious elements which can stick to and thus contaminate the surface ofa reflective material. Through the addition of a liquidphobic structure,for example a hydrophobic coating to the surface of a reflectivematerial, liquids are repelled from the surface, and thus liquids,including contaminants in the liquids, cannot reach and/or attach to thereflective surface.

For example, contact of a reflective substrate 102 (in this case alsocomprising a sub-micron-structured surface 108) with a liquid causesfouling on the surface, as in FIG. 2A and as shown with reference tospherical marker 302 in FIG. 3A, where contaminants/liquids 206 attachto the surface. Thus, as in FIG. 2A, light that is directed toward thereflective surface 202 cannot reflect back 204 at all portions of thereflective surface, effectively limiting the reflective properties ofthe substrate. Disposing a liquidphobic structure 104 on the surface ofthe reflective substrate limits or effectively eliminates this fouling,as shown in FIG. 2B and with reference to spherical marker 304 shown inFIG. 3A. Thus, as in FIG. 2B, light that is directed toward the surfacecan be reflected back away from the surface of the reflective substrate.

Suitably, the application of a liquidphobic structure to a reflectivesubstrate allows the substrate to maintain its reflective propertiesafter contact with a liquid. As used herein, the term “reflectiveproperties” refers to the ability of a surface to bounce back some orall of the light that strike the surface. This includes bouncing backall of the wavelengths of light that strikes a surface, as well asbouncing back at least some of the wavelengths of light that strike asurface. Thus, reflective properties refers to both the efficiency ofbouncing back light (i.e., the intensity that reflects back) as well asthe completeness of the spectrum that is reflected, i.e., the percentageof wavelengths that are bounced back. Suitably, the light is bouncedback to a receiver or detector. For example, FIG. 3B shows reflective asphere 306 that has been coated with a liquidphobic substrate andcontacted with a blood sample, sphere 308 that has not been treated witha liquidphobic substrate and has been soiled by contaminants from ablood sample, and a sphere 310 that has been treated with a liquidphobicsubstrate and not contacted with blood. As shown, sphere 306substantially maintains its reflective properties after being contactedwith a blood sample similar to sphere 310 which has not been contactedwith blood, while sphere 308 shows a significant degradation inreflective properties following such blood contact. In exemplaryembodiments, at least about 100% of the light that strikes a surface isbounced back, or at least about 95%, at least about 90%, at least about85%, at least about 80%, at least about 75%, at least about 70%, atleast about 65%, at least about 60%, at least about 55%, at least about50%, at least about 45%, at least about 40%, etc., of the light isbounced back from a substrate that comprises a submicron texturedsurface and a liquidphobic coating as described herein.

The addition of a liquidphobic structure to the surface of a reflectivesubstrate limits or prevents fouling on the surface of the substratesuch that the reflective substrate maintains at least about 50% of itsreflective properties after contact with a liquid. It is important thatthe liquidphobic structure does not significantly impair the reflectivecharacteristics of the reflective substrate. In suitable embodiments,the substrate reflects at least about 50% of the light that strikes asurface (i.e., maintains at least about 50% of its reflectiveproperties). More suitably, a substrate maintains at least about 55%, atleast about 60%, at least about 65%, at least about 70%, at least about75%, at least about 80%, at least about 85%, at least about 90%, atleast about 95%, at least about 99%, or about 100% of its reflectiveproperties. As used herein, the term “substantially maintain” as used torefer to the reflective characteristics of a reflective substrate isused to indicate that the substrate maintains at least about 50% of itsreflective properties after contact with a liquid.

In further embodiments, the present invention provides methods ofsubstantially maintaining the reflective properties of a reflectivesubstrate comprising disposing a liquidphobic structure on a surface ofthe substrate, wherein the reflective properties are substantiallymaintained after the substrate is contacted with a liquid.

As noted above, as in FIG. 1A, in suitable embodiments, a liquidphobicstructure is disposed directly onto the surface of the substrate.Exemplary reflective substrates are described throughout and includereflective films and marker dots, as well as reflective objects such asreflective spheres or cubes. As noted herein, liquidphobic structuresinclude hydrophobic, lipidphobic, hemophobic and amphiphobic structures.Suitably, the liquidphobic structures are hydrophobic coatings, such asperfluorinated organic coatings, for example, perfluorinated silanecoatings.

In exemplary embodiments, a liquidphobic structure, e.g., a hydrophobiccoating, is directly disposed (e.g., as in FIG. 1A) on the surface of areflective substrate. Methods for disposing such structures and coatingsinclude, but are not limited to, painting, spraying, layering, dipping,spin-coating, applying, evaporative deposition, etc. As shown in FIG.1B, suitably a liquidphobic structure, e.g., a hydrophobic coating, isdisposed on a sub-micron-structured surface 106.

Disposition of liquidphobic structures onto the surface of reflectivesubstrate 102 suitably requires that the surface of substrate 102comprise appropriate chemical groups so as to facilitate spreadingand/or bonding of the liquidphobic structures to the substrate. Forexample, in applications where a perfluorinated organic layer isdisposed on the substrate, chemically reactive groups that couple to thelayer are often required on the substrate, such as silanols on thesurface of a substrate onto which a layer of perfluorinated silane is tobe disposed, so as to facilitate silane coupling.

In additional embodiments, an adhesive layer can be applied to thesurface of the reflective material so as to facilitate interactionbetween the liquidphobic structures and the reflective material.

In still further embodiments, a sub-micron-structured surface, e.g., anano-structured surface, can first be generated on the surface of areflective substrate, and then a liquidphobic structure (e.g.,hydrophobic coating) can be disposed onto the sub-micron-structuredsurface. For example, as shown in FIG. 1C, where a reflective substrate102 comprises a sub-micron-structured surface, such as a nano-structuredsurface 108, which has been generated on the surface of the substrate.Liquidphobic structure 104 can then be disposed directly onto thesub-micron-structured/nano-structured surface 108 using any of themethods described herein. As discussed throughout, in suitableembodiments, various liquidphobic structures, including perfluorinatedorganic coatings, such as perfluorinated silane coatings, can bedisposed on the reflective substrates, sub-micron-structured surfacesand nano-structured surfaces. In general, the more structured a surface,or the higher the surface area of a reflective substrate, the lesslikely the surface will be prone to fouling after disposition of aliquidphobic structure (e.g., a hydrophobic coating).

Various methods can be used to generate a sub-micron structured surfaceon the reflective. Suitably, the sub-micron or nano-structured surfaceis optically clear. For example, a nanostructure, such as a nanowire,nanofiber, nanocrystal, nanorod, nanoparticle (e.g., a sphericalnanoparticle), nanosphere, nanotube, etc., can be generated on thesurface of the reflective material. In exemplary embodiments, ananofiber is generated on the surface of a reflective material.

As disclosed in U.S. Patent Application Pub. 20050181195 and U.S. patentapplication Ser. No. 11/869,508, filed Oct. 9, 2007, the disclosures ofeach of which are incorporated by reference herein in their entireties,nanofibers refer to elongated nanostructures, typically characterized byat least one cross-sectional dimension less than about 1000 nm, e.g.,less than about 500 nm, less than about 250 nm, less than about 100 nm,less than about 50 nm, less than about 40 nm, less than about 30 nm,less than about 20 nm, less than about 10 nm, or even about 5 nm orless. In many cases the region or characteristic dimension will be alongthe smallest axis of the structure. Nanofibers typically have oneprinciple axis that is longer than the other two principle axes and,thus, have an aspect ratio greater than one, an aspect ratio of 2 orgreater, an aspect ratio greater than about 10, an aspect ratio greaterthan about 20, and often an aspect ratio greater than about 100, 200,500, 1000, or 2000.

Nanofibers for use in the practice of the present invention suitablycomprise any of a number of different materials and can be fabricatedfrom essentially any convenient material or materials. In some typicalembodiments herein, the nanofibers of the invention comprise anon-carbon or inorganic material. Also, in some embodiments, thenanofibers comprise silicon or a silicon containing compound (e.g., asilicon oxide). In certain embodiments, the nanofibers range in lengthfrom about 10 nm to about 200 μm, or from about 20 nm to about 100 μm,or from about 20 nm or 50 nm to about 500 nm. Suitably the nanofiberswill be coated with a hydrophobic, lipophobic, amphiphobic or otherliquidphobic coating.

The term nanofiber can optionally also include such structures as, e.g.,nanowires, nanowhiskers, semi-conducting nanofibers and non-carbonnanotubes (e.g., boron nanotubes or nanotubules) and the like.Additionally, in some embodiments herein, nanocrystals or other similarnanostructures can also be used in place of more “typical” nanofibers toproduce liquidphobic surfaces. For example, nanostructures havingsmaller aspect ratios (e.g., than those described above), such asnanorods, nanotetrapods, nanoposts (e.g., non-silicon nanoposts), andthe like are also optionally included within the nanofiber definitionherein (in certain embodiments). Examples of such other optionallyincluded nanostructures can be found, e.g., in published PCT ApplicationNo. WO 03/054953 and the references discussed therein, all of which areincorporated herein by reference in their entirety for all purposes.

Suitably, nanofibers for use in the practice of the present inventionwill comprise semiconductor materials or semiconductor elements such asthose disclosed in U.S. patent application Ser. No. 10/796,832, andinclude any type of semiconductor, including group II-VI, group III-V,group IV-VI and group IV semiconductors. Suitable semiconductormaterials include, but are not limited to, Si, Ge, Sn, Se, Te, B, C(including diamond), P, BN, BP, BAs, AlN, AlP, AlAs, AlSb, GaN, GaP,GaAs, GaSb, InN, InP, InAs, InSb, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs,GaSb, ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTe, BeS, BeSe,BeTe, MgS, MgSe, GeS, GeSe, GeTe, SnS, SnSe, SnTe, PbO, PbS, PbSe, PbTe,CuF, CuCl, CuBr, CuI, Ge₃N₄, (Al, Ga, In)₂ (S, Se, Te)₃, Al₂CO, and anappropriate combination of two or more such semiconductors. In furtherembodiments, the nanofibers can comprise materials such as metals,polysilicons, polymers, insulator materials, etc. Suitable metalsinclude, but are not limited to, Pd, Pt, Ni, W, Ru, Ta, Co, Mo, Ir, Re,Rh, Hf, Nb, Au, Ag, Fe, Al, WN₂ and TaN. Suitable insulator materialsinclude, but are not limited to, SiO₂, TiO₂ and Si₃N₄.

Common methods for making nanofibers include vapor liquid solid growth(VLS), laser ablation (laser catalytic growth) and thermal evaporation.See, for example, Morales et al. (1998) “A Laser Ablation Method for theSynthesis of Crystalline Semiconductor Nanowires” Science 279, 208-211(1998). In one exemplary approach, a hybrid pulsed laserablation/chemical vapor deposition (PLA-CVD) process for the synthesisof semiconductor nanofibers with longitudinally ordered heterostructuresis used. See, Wu et al. (2002) “Block-by-Block Growth ofSingle-Crystalline Si/SiGe Superlattice Nanowires,” Nano Letters2:83-86.

In yet another approach, substrates and self assembling monolayer (SAM)forming materials can be used, e.g., along with microcontact printingtechniques to make nanofibers, such as those described by Schon, Meng,and Bao, “Self-assembled monolayer organic field-effect transistors,”Nature 413:713 (2001); Zhou et al. (1997) “NanoscaleMetal/Self-Assembled Monolayer/Metal Heterostructures,” Applied PhysicsLetters 71:611; and WO 96/29629 (Whitesides, et al., published Jun. 26,1996).

Growth of nanofibers, such as nanowires, having various aspect ratios,including nanowires with controlled diameters, is described in, e.g.,Gudiksen et al. (2000) “Diameter-selective synthesis of semiconductornanowires” J. Am. Chem. Soc. 122:8801-8802; Cui et al. (2001)“Diameter-controlled synthesis of single-crystal silicon nanowires”Appl. Phys. Lett. 78: 2214-2216; Gudiksen et al. (2001) “Syntheticcontrol of the diameter and length of single crystal semiconductornanowires” J. Phys. Chem. B 105:4062-4064; Morales et al. (1998) “Alaser ablation method for the synthesis of crystalline semiconductornanowires” Science 279:208-211; Duan et al. (2000) “General synthesis ofcompound semiconductor nanowires” Adv. Mater. 12:298-302; Cui et al.(2000) “Doping and electrical transport in silicon nanowires” J. Phys.Chem. B 104:5213-5216; Peng et al. (2000), supra; Puntes et al. (2001),supra; U.S. Pat. No. 6,225,198 to Alivisatos et al., supra; U.S. Pat.No. 6,036,774 to Lieber et al. (Mar. 14, 2000) entitled “Method ofproducing metal oxide nanorods”; U.S. Pat. No. 5,897,945 to Lieber etal. (Apr. 27, 1999) entitled “Metal oxide nanorods”; U.S. Pat. No.5,997,832 to Lieber et al. (Dec. 7, 1999) “Preparation of carbidenanorods”; Urbau et al. (2002) “Synthesis of single-crystallineperovskite nanowires composed of barium titanate and strontium titanate”J. Am. Chem. Soc., 124, 1186; Yun et al. (2002) “FerroelectricProperties of Individual Barium Titanate Nanowires Investigated byScanned Probe Microscopy” Nano Letters 2, 447; and published PCTapplication Nos. WO 02/17362, and WO 02/080280.

The present invention also optionally can be used with structures thatmay fall outside of the size range of typical nanostructures. Forexample, Haraguchi et al. (U.S. Pat. No. 5,332,910) describenanowhiskers which are optionally used herein. Semi-conductor whiskersare also described by Haraguchi et al. (1994) “Polarization Dependenceof Light Emitted from GaAs p-n junctions in quantum wire crystals” J.Appl. Phys. 75(8): 4220-4225; Hiruma et al. (1993) “GaAs Free StandingQuantum Sized Wires,” J. Appl. Phys. 74(5):3162-3171; Haraguchi et al.(1996) “Self Organized Fabrication of Planar GaAs Nanowhisker Arrays,and Yazawa (1993) “Semiconductor Nanowhiskers” Adv. Mater.5(78):577-579. Such nanowhiskers are optionally employed as thenanofibers components of the surfaces of the invention.

In still further embodiments, methods of generating asub-micron-structured surface on the surface of a reflective substrateinclude disposing a layer of micron-sized (e.g., 1 to 10s of mm) ornano-sized (e.g. 1 to 100s of nm) particles, for example, colloidalsilica or submicon silica microspheres (e.g., silica or fumed silicaparticles), on the substrate. Such particles can be disposed on thereflective substrate directly if the surface comprises the appropriatesurface charge, or the surface of the reflective substrate can be firsttreated to form an intermediate adhesion layer such that the surface ofthe substrate has the appropriate charge. For example, the surface of areflective material can be treated so as to generate a positive surface.Thus, in suitable embodiments, the present invention provides methods ofdisposing a liquidphobic structure on a reflective substrate comprisingdisposing a sub-micron-structured surface on the reflective substrateand disposing a liquidphobic structure on the sub-micron-structuredsurface.

For example, a glass surface which is negatively charged at pH 7 can becoated with polylysine or soluble alumina (or example, by soaking thesurface in such solutions) so as to render the surface positivelycharged at pH 7. Then, micro or nanoparticles, for example silica orfumed silica particles (negatively charged at pH 7), can be disposed onthe surface so as to adhere to the positively charged surface.

In further embodiments a thin, optically clear alumina layer can bedisposed on the surface of the reflective material, followed by thegeneration of a sub-micron-structured surface (including anano-structured surface). For example, the alumina layer can simply beheated, e.g., in a boiling liquid such as water, so as to form asub-micron or nano-structured surface. Generation of a sub-micron ornano-structured surface by heating can also be used directly onmaterials that comprise alumina or aluminum, for example, the surface ofreflective spheres (discussed in greater detail herein).

It should be noted that the surface of the reflective substrate can besmooth, or can comprise a sub-micron-structured (or micron-sized)surface already, prior to the addition of a sub-micron structuredsurface. In further embodiments, the surface of the reflective materialcan be roughened (so long as the roughening does not deleteriouslyaffect the reflective properties of the material) prior to the additionof a liquidphobic structure. Exemplary methods of roughening a surfaceinclude mechanical roughening, chemical roughening, etc.

Following the generation of a sub-micron-structured surface on areflective substrate, a liquidphobic structure can then be disposed onthe surface. As discussed herein, suitably the liquidphobic structure isa hydrophobic coating, including those described throughout. Exemplaryhydrophobic coatings include perfluorinated organic coatings. Thus, inexemplary embodiments, a perfluorinated silane layer can be disposed ona sub-micron-structured surface comprising silica or fumed silica.

As discussed herein, suitably the methods of the present inventionprovide reflective surfaces which are non-fouling such that at least 50%of the reflective properties of the reflective substrate are maintainedfollowing contact with a liquid (including biological fluids).

The present invention also provides various articles comprisingreflective substrates which have been coated with a liquidphobicstructure using the various methods described herein. For example, inone embodiment, the present invention provides a reflective spherecomprising a hydrophobic coating on a surface of the sphere, wherein thesphere substantially maintains its reflective properties after thesphere is contacted with a liquid.

In suitable embodiments, the reflective spheres comprise aperfluorinated organic coating, such as a perfluorinated silane. Such acoating can be directly disposed on the surface of the reflectivematerial, or can be disposed on a sub-micron-structured layer (e.g., alayer of silica particles) on the reflective material. As discussedthroughout, suitably the reflective sphere maintains at least about 50%of its reflective properties after contact with a liquid, for example abiological fluid.

The methods, objects and products of the present invention haveapplications in various areas. For example, reflective films, reflectivetapes, reflective fabrics and marker dots can be used in various methodsfor marking, locating and motion tracking Applications of reflectivemarker dots on fabrics can be used in crash-test dummy suits, inindustrial applications such as tracking time-in-motion studies, inmotion sensing spots or markers (e.g., reflective markers onfirefighter's uniforms), etc.

In additional embodiments, the reflective objects of the presentinvention, such as reflective spheres, can be used in biomedicalapplications. For example, reflective spheres can be used in medicalapplications such as in connection with surgical robotics and navigationsystems. In such applications, reflective spheres (or other shapedobjects) are placed on a surgical instrument or apparatus. Lightemitting diodes which emit light (e.g., infrared light), positioned withcameras, then shine light on the reflective spheres. The reflected lightis then captured by the camera and then fed to a computer, whichtranslates the information to form an anatomical map or positionaldiagram of the instrument. U.S. Pat. No. 6,351,659, the disclosure ofwhich is incorporated by reference herein in its entirety, describes onereferencing system that utilizes such reflective spheres. Thereferencing system operates with passive reflectors instead of activesignal emitters, this referencing system being employed for operations,including neurosurgical instruments and apparatus employed in theoperation. The system involves the application of a source of preferablyinfrared radiation, at least two mapping or referencing cameras and acomputer unit with a graphic display terminal connected to the cameras.The reflector referencing system comprises at least two reflectors whichcan be applied in a replaceable manner via adapters to instruments orapparatus employed in the operation, i.e. in an arrangement which isexclusively characteristic for this array of reflectors. Each surgicalinstrument reflects an image that can be sensed exclusively for theparticular instrument concerned.

Thus, in further embodiments, the present invention provides methods ofperforming a medical procedure using a surgical navigation system on apatient. The methods suitably comprise placing one or more reflectivespheres on a surgical instrument or apparatus. Suitably, the reflectivespheres comprise a liquidphobic coating (e.g., a hydrophobic coating) ona surface of the spheres. As described herein, the use of a liquidphobiccoating allow the spheres to substantially maintain their reflectiveproperties after the spheres are contacted with a biological fluid. Alight is then shined on the reflective spheres. Reflected light from thespheres is then captured with a camera or other suitable device. Thelocation and/or position of the spheres are then registering and/ortracked. Suitably, the relative locations and/or positions of any one ofa) the spheres, b) the patient's anatomy (e.g., location of bones, skin,organs, muscles, blood vessels, etc.) and/or c) the instrument or theapparatus are registered, thereby tracking the location and/or positionof the instrument, and/or the apparatus, and/or the patient's anatomywith respect to each other. Thus, the locations and/or positions of thevarious elements can be determined relative to one another such that ananatomical map of the patient, or a positional/locational diagram of theinstrument or apparatus can be prepared showing the instrument orapparatus in relation to a patient's anatomy, and/or in relation toitself.

As discussed throughout, suitably the reflective sphere comprises ahydrophobic coating comprising a sub-micron-structured surface on thesurface of the sphere and a hydrophobic coating disposed on thesub-micron-structured surface. Suitable hydrophobic coatings aredescribed throughout, including a perfluorinated organic coating. Inexemplary embodiments, the reflective sphere comprises asub-micron-structured layer of silica particles and a perfluorinatedsilane coating on the silica particles. As noted herein, suitably thereflective spheres substantially maintain their reflective propertiesafter contact with a biological fluid such that at least 70% of thereflected light (e.g., at least 80% or at least 90%) from the sphere iscaptured by the camera or other device.

Use of non-fouling reflective materials of the present invention caneliminate the need to clean or replace the reflective materials in thevarious applications, therefore saving time, for example in anindustrial (e.g., machine replacement) or surgical setting.

It will be readily apparent to one of ordinary skill in the relevantarts that other suitable modifications and adaptations to the methodsand applications described herein can be made without departing from thescope of the invention or any embodiment thereof. Having now describedthe present invention in detail, the same will be more clearlyunderstood by reference to the following examples, which are includedherewith for purposes of illustration only and are not intended to belimiting of the invention.

Exemplary embodiments of the present invention have been presented. Theinvention is not limited to these examples. These examples are presentedherein for purposes of illustration, and not limitation. Alternatives(including equivalents, extensions, variations, deviations, etc., ofthose described herein) will be apparent to persons skilled in therelevant art(s) based on the teachings contained herein. Suchalternatives fall within the scope and spirit of the invention.

All publications, patents and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent or patent application wasspecifically and individually indicated to be incorporated by reference.

What is claimed is:
 1. A reflective substrate comprising a liquidphobicstructure on a sub-micron structured surface of the substrate, whereinthe substrate substantially maintains its reflective properties afterthe substrate is contacted with a liquid.
 2. The reflective substrate ofclaim 1, wherein the substrate is a reflective film, fabric, tape orreflective marker dot.
 3. The reflective substrate of claim 1, whereinthe substrate is a reflective sphere or cube.
 4. The reflectivesubstrate of claim 1, wherein the substrate is a retroreflectivesubstrate.
 5. The reflective substrate of claim 1, wherein theliquidphobic structure comprises a hydrophobic coating.
 6. Thereflective substrate of claim 5, wherein the hydrophobic coatingcomprises a super-hydrophobic coating.
 7. The reflective substrate ofclaim 5, wherein the hydrophobic coating is disposed on the sub-micronstructured surface of the substrate.
 8. The reflective substrate ofclaim 5, wherein the hydrophobic coating comprises perfluorinatedorganic.
 9. The reflective substrate of claim 1, wherein the substratemaintains at least 70% of its reflective properties after contact with aliquid.
 10. The reflective substrate of claim 1, wherein the substratemaintains its reflective properties after contact with a biologicalfluid.
 11. A reflective sphere comprising a hydrophobic coating on asub-micron structured surface of the sphere, wherein the spheresubstantially maintains its reflective properties after the sphere iscontacted with a liquid.
 12. The reflective sphere of claim 11, whereinthe hydrophobic coating comprises a perfluorinated organic.
 13. Thereflective sphere of claim 11, wherein the surface of the sphere furthercomprises a sub-micron-structured layer of silica particles and aperfluorinated silane hydrophobic coating.
 14. The reflective sphere ofclaim 11, wherein the sphere maintains at least 70% of its reflectiveproperties after contact with a liquid.
 15. The reflective substrate ofclaim 11, wherein the sphere maintains its reflective properties aftercontact with a biological fluid.